1. Field of the Invention
The present invention relates to an automobile power plant apparatus. The automobile power plant apparatus is the part of an automobile which transmits the engine driving forces to the wheels.
2. Description of the Prior Art
As illustrated in the upper half of FIG. 7, an automobile power plant includes an engine 1, a transmission 2 connected to an output side of the engine 1 in series in a vehicle lengthwise direction "Y," a propeller shaft 3 connected to an output shaft of the transmission 2 at an end thereof in the vehicle lengthwise direction "Y," a front mount 4 elastically supporting the engine 1, a rear mount 5 elastically supporting a lower part of the transmission 2 at around an end 2a of the transmission 2, and a body 6. The body 6 is provided with the engine 1, the transmission 2, the propeller shaft 3, the front mount 4 and the rear mount 5. Further, the propeller shaft 3 is provided with universal joints 3a and 3b at its ends, respectively.
In the conventional automobile power plant apparatus, the rear mount 5 supports at around the end 2a of the transmission 2. This is mainly because the transmission 2 has a relatively small dimension "H" in a vertical direction at around the end 2a, and it accordingly is easy to provide a space for installing the rear mount 5.
In the conventional automobile power plant apparatus, when the engine 1 is running at a high speed, flexural vibrations enlarge, there arise phenomena like vibrations of the body 6 and noises, and consequently such phenomena escalates. The flexural vibrations consist of vertical components and horizontal components, and it is especially important to suppress the vertical components of the flexural vibrations in order to relieve the phenomena such as the vibrations of the body 6 and the noises.
In the lower half of FIG. 7, there is illustrated a basic characteristic of resonant mode accompanied by the flexural vibrations when the engine 1 is running at a high speed. As can be seen from the lower half of FIG. 7, since the engine 1 and the transmission 2 have a high rigidity, the boundary area between the engine 1 and the transmission 2 comes to have a low rigidity. Accordingly, it is likely to vibrate at the boundary area between the engine 1 and the transmission 2, and the boundary area corresponds to a vibrational loop "P1." Since the universal joints 3a and 3b have a low rigidity, they correspond to vibrational loops "P2" and "P3" respectively. Since the front mount 1 is placed near a position which corresponds to a vibrational node "P4," vibrations are hardly input into the front mount 1.
In the conventional automobile power plant apparatus, since there arise large amplitudes at around the end 2a of the transmission 2 and since the end 2a of the transmission 2 is elastically supported by the rear mount 5, as illustrated in the resonant mode the lower half of FIG. 7, the vibrations are transmitted increasingly to the body 6. As a result, such a construction is likely to cause disturbing noises which sound like oppressing to the ears of the passengers.